Capacitors are electrical devices which store and release electrical energy. A capacitor will include at least one pair of electrodes separated, typically by a relatively small distance, by a body of dielectric material. Charge is stored in the capacitor by polarizing the device so that one of the electrodes, referred to as a cathode or negative electrode, will have a net negative charge, and the other electrode, referred to as an anode or positive electrode, will have a net positive charge. The body of dielectric material prevents charge from migrating between the electrodes. Capacitors may be fabricated in a variety of configurations. In some embodiments, a plurality of pairs of positive and negative electrodes are disposed in an interleaved negative-positive relationship. In other instances, a single pair of electrodes, each comprising a relatively large body of thin, flexible material, together with a flexible dielectric material, are disposed in a rolled relationship so as to form a capacitor device.
Capacitors can store, and rapidly release, relatively large amounts of energy. Because of their high current capacity, capacitors are used in a variety of electrical systems. For example, capacitors are used in communications devices such as radios and cellular telephones for the purpose of providing a high burst of power for initiating broadcast of a transmission. Capacitors are also used to provide power for starting electrical motors and energizing flash lamps and lasers. The high current capability of capacitors also makes them useful in specialized military systems including armor and munitions.
Capacitors of the type used for delivery of relatively high levels of power are generally fairly large bulky items, and their size and weight can impose a significant design constraint on systems, particularly portable systems, in which they are included. Heretofore, these size and weight constraints have limited the utility and practicality of particular systems. As will be described in detail hereinbelow, the present invention recognizes that by the appropriate selection of materials, capacitors may be manufactured which combine good structural properties such as strength and stiffness together with good electrical properties. Such capacitors may actually form structural elements of systems in which they are incorporated, and hence these capacitors are referred to herein as “structural capacitors.” Since structural capacitors function both as capacitive storage devices as well as structural components of systems, the weight and/or size burden imposed upon such systems by the need for capacitive storage is greatly minimized. In this regard, the structural capacitors of the present invention may function as circuit boards, housings, casings, protective members, and the like. Further details and advantages of the present invention will be apparent from the drawings, discussion and description which follow.